Hydraulic motor cylinder with stroke limiting valve



C- B. LIVERS Feb. 26, 1952 HYDRAULIC MOTOR CYLINDER WITH STROKE-LIMITING VALVE Filed June 19, 1950 m m a E L B. s c. w 32$ @n n ww mmw w Q Q R N MN a a E w & mm N Q Q J M Kw l m \M m mm J M 7 I \M. NM. QM. \WWMRA HT.

ATTORNEY Patented Feb. 26, 1952 HYDRAULIC MOTOR CYLINDER WITH STROKE LIMITING VALVE Carlos B. Livers, North Hollywood, Calif., as-

signor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application June 19, 1950, Serial No. 168,913

7 Claims. 1

This invention relates to motor cylinders such as are used in hydraulic systems for raising and lowering earth-working elements of tractordrawn implements. It is frequently desirable to preset such cylinders for movement through a definite stroke and cause them to automatically .stop in a desired position without attention from the operator.

An object of the invention is to provide a unitary motor cylinder and stroke-limiting valve assembly in which the moving parts are substantially enclosed and protected from dirt and from mechanical injury.

Another object is to provide an assembly of this type in which the external fluid connections are both made at the same end of the cylinder.

Another object is to provide a motor cylinder with automatic stroke-limiting valve action that is reliable and is not subject to damage or to being thrown out of adjustment by failure to stop at the intended position.

Other more specific objects and features of the invention will become apparent from the following description, with reference to the drawing, in which:

Fig. 1 is a longitudinal sectional view through a cylinder assembly in accordance with the invention;

Fig. 2 is a cross-section taken in the plane II--II of Fig. 1; and

Fig. 3 is a cross-section taken in the plane IIIIlI of Fig. 1.

Referring to Fig. 1, the assembly therein disclosed comprises a cylinder l closed at its right end by a first head H, and at its left end by a second head l2. The heads II and [2 have internal flanges I3 and I4 that fit into the ends of the cylinder l0 and are sealed with respect thereto by sealing rings l5 and 16 respectively. The heads are held against the ends of the cylinder ID by four stay bolts [8 which are threaded into the second head I2.

The cylinder Ill contains a piston 20 to which is attached a piston rod 2| that extends through an aperture provided therefor in the first head II, the piston rod being sealed with respect to the head by a sealing ring 22. The head l2 has a projection 23 containing an eye 24 for-anchoring the cylinder to a suitable support, and the piston rod 2| is shown provided with a clevis 25 for connecting it to a device to be operated.

Fluid connections for supplying and exhausting fluid from either end of the cylinder are provided in the second head 12. Thus one port 36 in the second head I2 is connected by a passage 21 in the head, and by a valve seat passage 28, to a recess 29 in the interior of the head l2 which is in open communication with the left end of the cylinder I0.

Another port 30 in the head I2 is connected by the passage 3! in the head with the left end of a tube 32 which extends between the tube heads l2 and I I and is sealed with respect thereto by gaskets 33 and 34. The right end of the tube 32 communicates with a passage 35 in the head I! which is in open communication with the right end of the cylinder I0. Normally the valve passage 28- is open, so that by supplying pressure fluid to the port 26 and exhaust fluid from the port 30, the piston 20 is moved from left to right, whereas if pressure fluid is sup plied to port 30 and fluid is exhausted from port 26, the piston 20 is moved from right to left.

It is desired to limit the movement of the piston 20 in leftward direction, and to this end a valve mechanism is provided which closes 01? the passage 28 when the piston 20 has moved into the desired leftmost position.

This valve mechanism includes a poppet valve 3? adapted to seat against a seat 38 at the inner end of the valve passage 28 and thereby close the passage. The poppet 31 is guided in its movement by two integrally formed valve stems 39 and 40 projecting in opposite directions from thepoppet. The valve stem 40 projects into a bushing 4| that is positioned in a bore formed therefor in the head 12 and held in place by a split retaining ring 42. A helical compression spring 43 compressed between the poppet 31 and the inside face of the bushing 4| retains the latter in position against the retaining ring 42.

The bushing Al is sealed in its passage in the head by a sealing ring 64, and the valve stem 40 is sealed With respect to the bushing by a sealing ring 45. The valve stem 39 extends through a bore provided therefor in the head l2 into a cam chamber M that is formed in the head, the stem 39 being sealed by a seal 48. The cam chamber 41 is closed by a plate 49 that is vented to atmosphere as by the vent hole 50.

The cam chamber 41 contains a cam 52 that is secured to the left end of a push rod 53 that extends through an aperture provided therefor between the cam chamber 41 into the tube 32. A sealing ring 54 prevents leakage of fluid from the interior of tube 32 into the cam chamber 41.- The push rod 53 extends through the tube 32, and has an enlarged right end portion 53A that extends through an aperture provided therefor in the first head I I, and projects beyond the head a short distance. A sealing ring 55 prevents leakage of fluid past the portion 53A of the push rod where it passes through the head I l.

The push rod 53 and the cam 52 are normally maintained in a rightmost position, as shown in Fig. 1, by a helical compression spring 51 that is- 'compressed between the cam chamber closure plate 49 and the cam 52. In this position, the high portion of the cam depresses the valve stem 39 to hold the poppet 31 off of the seat 38 and permit free flow of fluid-through the passage 28.

The push rod 53 is actuated to shift the cam 5'2 and permit the poppet valve3'l"to close, by a pusher member 66 that is adjustably secured to the piston rod 2|. This pusher member 60 is clamped onto the "piston rod by a screw 6! and can be adjusted at any desired point along the rod by loosening the screw 6|.

The operation of the device is obviousfrom the drawing, but it will be briefly reviewed.

Normally the poppet 31 is held open by the cam 52, as shown in Fig.1, and'the piston 20 can be moved in either direction by supplying pressure fluid to one of the ports "25' or'3'0, and exhausting fluid from the other port. However, as the piston 20 approaches its'desired leftmost position, the pusher Gil contacts the right end of the push rod 53 and moves it to the left, compressing the sp ririg 51 in so doing. This causes the high part of the cam 52 to ride oil the end of the'valve stem 39, permitting the compression spring '43 to close the poppet 31 against the seat38. of the piston 20, as described, fluid is being exhausted from theleft end'of cylinder l0 through the-valve passage 28. Hence the pressure of the fluid tends to hold the poppet 3'! against its seat, and the spring 43 does not have to exert alarge force. 'When :it is next desired to move the piston 20 to-the right, the application of the pressure fluid to the port 26 opens the poppet -B'I- byvirtueof the fluid pressure, which is able *to overcome the-spring 43 and the load on the piston 20. As the pusher 63 is carried to theIight, it permits thepushrod 53 to be restored by the spring-51 to IIOITmaIyDOSi-tiOII, in whicn -the'high portion of the cam 52 holds the stem 39in position to maintain the poppet 31 clearof its seat 38.

The'spring 51 is relatively strong as compared to thespring 43, and .is able to open the poppet 31 against the force exerted by the spring 43 if the pusher 60 .is moved, along with the piston 20 and: piston rod 2|, tothe right by external force instead of by pressure fluid introducedthrough the port'26. Depression of thepush rod 53 by the pusher 6E3 positively blocks fluid flow out of the left 'end of the cylinder ill, and thereby prevents further movementof-thepiston Zll to the left, even though great -forceis applied from an. external'source to the piston rod 21. However, the.system does not prevent subsequent movement ofuthe piston tothe right when such movement is desired.

The spring 43 need only have enough strength to overcome the friction of the packing rings 45 and '48.

Since the push rod 53 does not applyforceto thepoppet3'l to close it directly; but, instead, simply moves the cam 52 outof the'way of the valve stem 39 to. permit the spring 43 to close the poppet 31, no damage to the valve assembly can be produced by slight excess movement of the pusher 60 to the left beyond the desired Of course during leftward movement stopping point. Such movement merely carries the cam 52 a little farther than it would normally move and further compresses the cam spring 51.

It will be observed that the only external moving parts on the assembly are the piston rod 2! and the projecting end-of the pushrod: 53. Furthermore,'the tube 32 not only serves as an enclosure for the rod 53 but provides a fluid connection between the two heads II and 12 so that both fluid, ports for external connection are in thesame .head, and in the head that has least movement when the cylinder assembly is supportediby. the eye"24,'which permits greater oscillatory movement. of the right end of the cylinder than the left.

Therigl'i t' end.portion 53A of rod 53 which passes through the seal 55 is made of larger diameter than the portion 53B of the rod passing through seal 54, to provide a hydraulic pressure force on the rod'53 aiding the 'spring'5l. When the pressure in the tube 32 islow, the seals 54 and 55 offer relatively low frictional resistance to movement, which "is readily overcome by the spring 51. However, if at the time the piston 23 is'moved to the right, a high back pressure exists in the tube 32, the friction at the seals 54 and- 55 can be quitegreat, and it is desirable to provide. a force aiding that of' the springv 5'3 but proportional to the pressureiin the tube "32, to compensate for the additional. frictional loading at the seals produced by the pressure. This pressure iorce is proportional .to thedifierential area of the rod portions 53B-and 53Av respectively.

The valvestems 39- and 40 are of the same diameter and are both exposed to atmospheric pressure on theirouter-ends. Therefore the forces acting on the valve 31- arexnot affected by the pressure withini-the "left end of'the cylinder l0 when the valve isin openrposi'tion.

Although for the purpose "of explaining the invention, a particularembodiment thereof has been showniand described, obvious-modifications will occur to a person skilled in the art, and I do not desire 'tobe'limited to the-exact details shown and described.

I claim:

1. A hydraulicmotor unit comprising: a cylinder having a firsthead at one end and a second head at theother "end said first'head having a piston rod passage therethroughga piston in said cylinder 1 and a "piston rod extending from said piston through said passage in said 'first head; said fi-rst head having aflrst' fluid-passage therein for supplyingfluid to andexhausting fluid from said one end 'of-said cylinder; said-second head having a 'second fluid pa'ssage therein-for supplying'fiuid' to and exhausting fluid from said other endof said cylinder;:said.second fluid passage including a valve: :seat facing; the: cylinder end. of the passage; a poppet valve'slicleably' supported in 'said second head for' movement :into. and out of closingengagement with saidseat; apush rod parallel .to said .CYIiIld6YrEDdLh3Vi-HQ' av first end extending beyond-said first 'head and a second end adjacent said poppet valve in saidsecond head; means insaid heads for slideably, supporting said push rod-.i-or longitudinal :movement; a pusher member on saidpiston mod engageable with said first end-ol saidpush rod-for shifting the-push rod from-itssaid:normalposition into an actuated position in response to inward move-v ment. of said piston rod -.into,. a predetermined position;.means responsive to movement of said push rod from its normal to its actuated position for seating said poppet valve; and means for restoring said push rod to its said normal position in response to opening movement of said poppet valve and outward movement of said piston rod from said predetermined position.

2. A unit according to claim 1 including a tube surrounding said push rod and extending between and sealing with said heads, said first fluid passage in said first head communicating with the adjacent end of said tube; said second head having an external port communicating with the other end of said tube, and fluid sealing means in each head sealing with said push rod for preventing leakage of fluid from said tube past said rod.

3. A unit according to claim 2 in which the portion of said push rod extending through said first head is of larger diameter than the portion extending through said second head.

4. A unit according to claim 1 in which said second head defines a chamber vented to atmosphere enclosing said second end of said push rod, said poppet valve has stems projecting from opposite sides thereof, said second head has alined guide passages for said valve stems extending from said second fluid passage to said chamber and to the exterior surface of said head respectlvely, and fluid-sealing means sealing said stems with respect to said guide passages.

5. A unit according to claim 1 in which said poppet valve has a stem extending transversely into operative relation with said second end of said push rod, a valve stem guide passage in said second head in which said stem is reciprocable, and fluid-sealing means between said valve stem and said guide passage.

6. A unit according to claimvl in which said means for seating said poppet valve comprises a' cam on said second end of said push rod and a spring urging said poppet toward its seat.

7. A unit according to claim 6 in which said means for restoring said push rod to its said normal position comprises a spring.

CARLOS B. LIVERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,383,689 Silver Aug. 28, 1945 2,509,589 Deardorfi May 30, 1950 

